#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
typedef long long ll;
using namespace std;
struct rabbit {
    ll juli;
    ll shijian;
};
bool cmp (rabbit a, rabbit b){
    return a.shijian-a.juli<b.shijian-b.juli;
}
int main() {
    int n,m,p;
    scanf("%d%d%d", &n, &m, &p);
    ll juli[n+1];
    juli[0]=0;
    ll z;
    for (int i=1; i<n; i++) {
        scanf("%lld", &z);
        juli[i]=z+juli[i-1];
    }
    rabbit rab[m];
    int num;
    ll time;
    for (int i=0; i<m; i++) {
        scanf("%d%lld", &num, &time);
        rab[i].juli=juli[num-1];
        rab[i].shijian=time;
    }
    sort(rab, rab+m, cmp);
    ll dp[p+1][m+1];
    memset(dp, 0x3f, sizeof(dp));
    rabbit biaoji=rab[m-1];
    dp[0][0]=0;
    ll cnt=0;
    for (int i=1; i<=m; i++) {
//        cout<<rab[i-1].juli<<"---"<<rab[i-1].shijian<<endl;
        dp[0][i]=biaoji.shijian-biaoji.juli+rab[i-1].juli-rab[i-1].shijian;
        cnt+=dp[0][i];
    }
    ll res=cnt;
    int st=0,end=0;
    for (int i=1; i<p; i++) {
        st=end;
        for (int j=st+1; j<=m; j++) {
            if (cnt-(j-st)*dp[0][j]<dp[i][j-1]) {
                dp[i][j]=cnt-(j-st)*dp[0][j];
                res=dp[i][j];
//                cout<<"res:"<<res<<endl;
                end=j;
            }
            else {
                cnt=dp[i][j-1];
                break;
            }
        }
    }
/*    for (int i=0; i<p; i++) {
        for (int j=0; j<=m; j++) cout<<dp[i][j]<<' ';
        cout<<endl;
    } */
    printf("%lld\n", res);
    return 0;
}
